Seroprotective groups among isolates of Borrelia burgdorferi

Development of Organoids to Study Infectious Host Interactions

Emerging organoid research is paving way for studies in infectious diseases. Described here is a technique for the generation of stem-cell derived organoids for human small intestine and lung together with methods to infect such organoids with a mock pathogen (Cryptosporidium parvum). Such systems are amenable to imaging and processing for molecular biological analyses. It is the intent of this chapter to provide a simple, routine organoid procedure so that in vitro studies with Borrelia such as cell invasion and dissemination can be conducted.

Infection history of the blood-meal host dictates pathogenic potential of the Lyme disease spirochete within the feeding tick vector

Lyme disease in humans is caused by several genospecies of the Borrelia burgdorferi sensu lato (s.l.) complex of spirochetal bacteria, including B. burgdorferi, B. afzelii and B. garinii. These bacteria exist in nature as obligate parasites in an enzootic cycle between small vertebrate hosts and Ixodid tick vectors, with humans representing incidental hosts. During the natural enzootic cycle, infected ticks in endemic areas feed not only upon naïve hosts, but also upon seropositive infected hosts. In the current study, we considered this environmental parameter and assessed the impact of the immune status of the blood-meal host on the phenotype of the Lyme disease spirochete within the tick vector. We found that blood from a seropositive host profoundly attenuates the infectivity (>104 fold) of homologous spirochetes within the tick vector without killing them. This dramatic neutralization of vector-borne spirochetes was not observed, however, when ticks and blood-meal hosts carried heterologous B. burgdorferi s.l. strains, or when mice lacking humoral immunity replaced wild-type mice as blood-meal hosts in similar experiments. Mechanistically, serum-mediated neutralization does not block induction of host-adapted OspC+ spirochetes during tick feeding, nor require tick midgut components. Significantly, this study demonstrates that strain-specific antibodies elicited by B. burgdorferi s.l. infection neutralize homologous bacteria within feeding ticks, before the Lyme disease spirochetes enter a host. The blood meal ingested from an infected host thereby prevents super-infection by homologous spirochetes, while facilitating transmission of heterologous B. burgdorferi s.l. strains. This finding suggests that Lyme disease spirochete diversity is stably maintained within endemic populations in local geographic regions through frequency-dependent selection of rare alleles of dominant polymorphic surface antigens.

Hamster and murine models of severe destructive Lyme arthritis

Arthritis is a frequent complication of infection in humans with Borrelia burgdorferi. Weeks to months following the onset of Lyme borreliosis, a histopathological reaction characteristic of synovitis including bone, joint, muscle, or tendon pain may occur. A subpopulation of patients may progress to a chronic, debilitating arthritis months to years after infection which has been classified as severe destructive Lyme arthritis. This arthritis involves focal bone erosion and destruction of articular cartilage. Hamsters and mice are animal models that have been utilized to study articular manifestations of Lyme borreliosis. Infection of immunocompetent LSH hamsters or C3H mice results in a transient synovitis. However, severe destructive Lyme arthritis can be induced by infecting irradiated hamsters or mice and immunocompetent Borrelia-vaccinated hamsters, mice, and interferon-gamma- (IFN-γ-) deficient mice with viable B. burgdorferi. The hamster model of severe destructive Lyme arthritis facilitates easy assessment of Lyme borreliosis vaccine preparations for deleterious effects while murine models of severe destructive Lyme arthritis allow for investigation of mechanisms of immunopathology.

Significant differences between the Borrelia-infection and Borrelia-vaccination and -infection models of Lyme arthritis in C3H/HeN mice

The immunological events leading to the development of Lyme arthritis in humans are partially understood. Much of this information has been gained by studying the course of infection of naïve or vaccinated mice with Borrelia burgdorferi. However, the Borrelia-vaccination and -infection model has not been described using the organismal parameters commonly used in the widely accepted Borrelia-infection model. This is the first comparison between the Borrelia-infection and the Borrelia-vaccination and -infection models of arthritis. Borrelia-vaccinated and -infected C3H/HeN mice develop acute inflammation comparable to that of nonvaccinated, Borrelia-infected C3H/HeN mice. The duration and severity of arthritis in Borrelia-vaccinated and -infected mice was slightly increased compared with Borrelia-infected mice. Significantly, Borrelia-vaccinated and -infected C3H/HeN mice produce interleukin-17 (IL-17), while Borrelia-infected mice that had not been previously vaccinated do not. Neutralization of IL-17 in Borrelia-vaccinated and -infected C3H/HeN mice decreased the severity of arthritis, although not to the degree we observed previously in C57BL/6 mice. Collectively, these findings show that the Borrelia-vaccination and -infection model of Lyme arthritis incorporates elements of adaptive immunity that likely have relevance to human disease, but may not be observed in Borrelia-infected C3H/HeN mice.

Interleukin-23 is required for development of arthritis in mice vaccinated and challenged with Borrelia species

We recently hypothesized that T helper 17 (Th17) cells and their associated cytokines are involved in the development of arthritis following infection with Borrelia burgdorferi. Here, we show that interleukin-23 (IL-23), a survival factor for Th17 cells, is required for the induction of arthritis in mice vaccinated with B. burgdorferi strain 297 and challenged with "Borrelia bissettii." When Borrelia-vaccinated and -challenged mice were given antibodies to the p19 subunit of IL-23, they failed to develop the histopathological changes observed in untreated vaccinated and challenged mice. In addition, viable B. bissettii organisms stimulated the secretion of IL-17 from Borrelia-immune lymph node cells during in vitro culture. When anti-IL-23 p19 antibody was included in cultures of B. bissettii organisms and Borrelia-immune lymph node cells, the production of IL-17 was reduced to levels observed in cultures containing immune cells alone. Taken together, these results support the hypothesis that Th17 cell-associated cytokines are involved in the development of Borrelia-mediated arthritis. These findings provide insight into previously overlooked immune mechanisms responsible for the development of Lyme arthritis.

Role of IL-17, transforming growth factor-beta, and IL-6 in the development of arthritis and production of anti-outer surface protein A borreliacidal antibodies in Borrelia-vaccinated and -challenged mice

We showed recently that the adaptive immune events leading to the development of arthritis in Borrelia burgdorferi isolate 297-vaccinated and Borrelia bissettii-challenged mice involve IL-17. Here, we show in Borrelia-vaccinated and -challenged mice that two cytokines known to induce the production of IL-17, IL-6 and transforming growth factor (TGF)-beta, are also involved in the development of arthritis. Vaccinated and challenged mice administered either anti-TGF-beta or anti-IL-6 antibodies developed histopathologic changes of the hind paws similar to or greater than untreated control mice. By contrast, simultaneous blockage of these cytokines reduced the severity of arthritis in Borrelia-vaccinated and -challenged mice. Moreover, administration of anti-IL-17 antibodies to these dual-antibody-treated mice completely prevented the development of histopathologic changes of the ankle joints, significantly reduced edema of the hind paws, and prevented the production of anti-outer surface protein A borreliacidal antibodies. These findings demonstrate a role for the combined effects of IL-17, IL-6, and TGF-beta in the adaptive immune events leading to the development of Borrelia-induced arthritis.

Anti-CD25 antibody treatment of mice vaccinated and challenged with Borrelia spp. does not exacerbate arthritis but inhibits borreliacidal antibody production

CD4(+) CD25(+) T cells are a population of regulatory T cells responsible for the modulation of the immune response in several autoimmune and infectious disease models. We previously showed that adoptive transfer of enriched CD4(+) CD25(+) T cells also plays a major role in the prevention of arthritis in Borrelia-vaccinated (Borrelia burgdorferi isolate 297) and -challenged (B. bissettii) mice. Here, we present evidence that administration of anti-CD25 antibody at the time of challenge or at later intervals fails to enhance the development of severe destructive osteoarthropathy in Borrelia-vaccinated C57BL mice. However, Borrelia-vaccinated and -challenged mice receiving anti-CD25 antibody developed decreased borreliacidal antibody titers compared to vaccinated and challenged controls. These findings suggest that additional mechanisms besides CD4(+) CD25(+) T cells are involved in the regulation of the immune response to Borrelia infection following vaccination.

Experimental infection of dogs with Borrelia burgdorferi sensu stricto using Ixodes scapularis ticks artificially infected by capillary feeding

Specific pathogen-free dogs were experimentally infected with Borrelia burgdorferi sensu stricto using nymphal or adult female Ixodes scapularis ticks artificially infected with spirochetes by capillary feeding. The ticks were capillary fed B. burgdorferi isolate 610, previously isolated from a dog with Lyme disease and grown in BSK medium. This isolate induced clinical signs in the dogs similar to those for dogs infested with ticks naturally infected with B. burgdorferi. Adult ticks were more efficient than nymphs in transmitting spirochetes to the dogs. One of five dogs infested with nymphal ticks capillary fed B. burgdorferi was skin biopsy culture and serologically positive, and demonstrated lameness. In contrast, all five dogs infested with adult female ticks that had been capillary fed with B. burgdorferi were culture and serologically positive, with one dog developing lameness. The immunoblot profiles of dogs challenged with female ticks infected by capillary feeding (8 weeks post challenge) were similar to immunoblots (4 weeks post challenge) from dogs challenged with naturally infected females collected in the field. These studies demonstrated that B. burgdorferi cultured in BSK medium can be capillary fed to either nymphal or adult female ticks under laboratory controlled conditions for the purpose of transmitting the spirochete to dogs during the tick's blood meal. This tick infection system would be useful for a controlled and defined challenge of vaccinated and non-vaccinated dogs for proper evaluation of vaccine efficacy, which is difficult to achieve using field-collected ticks. Furthermore, this system may also be useful for investigation of the pathogenesis of Lyme disease, evaluation of the pathogenicity of new isolates of B. burgdorferi, or evaluation of antibiotic therapy.

An ospA-polymerase chain reaction/restriction fragment length polymorphism-based method for sensitive detection and reliable differentiation of all European Borrelia burgdorferi sensu lato species and OspA types

We describe a sensitive and reliable method for detection and differentiation of the five relevant European Borrelia burgdorferi sensu lato species ( B. burgdorferi sensu stricto, B. afzelii, B. garinii, B. valaisiana, and B. lusitaniae), based on a heminested ospA-PCR followed by restriction enzyme analysis. Sensitivity was one borrelia per PCR except for B. afzelii, where it was five per PCR. None of seven relapsing fever borreliae, eight Leptospira serovars or two Treponema species were amplified. Except B. garinii, each of the five B. burgdorferi s.l. species is represented by one or two characteristic restriction fragment length polymorphism (RFLP) patterns. Analysis of the heterogeneous group of B. garinii resulted in five different RFLP patterns, corresponding to the OspA types 3-7 associated with this species. In a pilot study on 529 Ixodes ricinus ticks from three different regions in Southern Germany, all species and OspA types were found except B. lusitaniae and B. garinii OspA type 7, arguing for a broad distribution of almost all OspA types. A further notable finding was the focal prevalence of OspA type 4, which has rarely been detected in ticks previously. Thus, the developed method provides a fast and simple tool for epidemiological studies on the heterogeneity of species and OspA types in Europe which has important implications for the development of vaccines and (microbiological) test systems for Europe.

Homologous and heterologous Borrelia burgdorferi challenge of infection-derived immune rabbits using host-adapted organisms

We have recently found that strain B31 infection-immune rabbits are completely protected against homologous challenge with large numbers (>10(6)) of host-adapted Borrelia burgdorferi (HAB) (E. S. Shang, C. I. Champion, X. Wu, J. T. Skare, D. B. Blanco, J. N. Miller, and M. A. Lovett, Infect. Immun. 68:4189-4199, 2000). In this study, we have extended these findings to determine whether B31 strain infection-immune rabbits are also protected against heterologous HAB challenge. Infection-immune rabbits challenged with large numbers (>10(6)) of homologous HAB strain B31 were completely protected from erythema migrans (EM) and skin and disseminated infection. In contrast, infection-immune rabbits challenged with heterologous HAB strains N40 and Sh-2-82 were completely susceptible to EM and skin and disseminated infection; challenge with strain 297 also resulted in EM and infection of the skin and viscera, but clearance of infection occurred 3 weeks postchallenge. These findings confirm that immunity elicited in rabbits by B31 strain infection confers complete protection against large-dose homologous HAB challenge but not against a heterologous strain.

Specificity of infection-induced immunity among Borrelia burgdorferi sensu lato species

The specificity of infection-induced immunity in mice infected with cultured or host-adapted Borrelia burgdorferi sensu lato, the agent of Lyme disease, was examined. Sera obtained from mice following infection with high and low doses of cultured B. burgdorferi sensu stricto, transplantation of infected tissue (host-adapted spirochetes), or tick-borne inoculation all showed protective activity in passive immunization assays. Infection and disease were similar in mice infected with cultured spirochetes or by transplantation. Thus, the adaptive form of inoculated spirochetes did not influence the immune response during active infection. Mice infected with B. burgdorferi sensu stricto and then cured of infection with an antibiotic during early or late stages of infection were resistant to challenge with high doses of homologous cultured spirochetes for up to 1 year. In contrast, actively immune mice infected with different Borrelia species (B. burgdorferi sensu lato, B. burgdorferi sensu stricto cN40, Borrelia afzelii PKo, and Borrelia garinii PBi) and then treated with an antibiotic were resistant to challenge with cultured homologous but not heterologous spirochetes. Similar results were achieved for actively immune mice challenged by transplantation and by passive immunization with sera from mice infected with each of the Borrelia species and then challenged with cultured spirochetes. Arthritis and carditis in mice that had immunizing infections with B. afzelii and B. garinii and then challenged by transplantation with B. burgdorferi sensu stricto were equivalent in prevalence and severity to those in nonimmune recipient mice. These results indicate that protective immunity and disease-modulating immunity that develop during active infection are universal among species related to B. burgdorferi sensu lato but are species specific.

Experimental infection of cattle with several Borrelia burgdorferi sensu lato strains; immunological heterogeneity of strains as revealed in serological tests

Twenty-three experimental cattle, mainly calves, were each inoculated 1-3 times with one of ten Finnish Borrelia burgdorferi sensu lato strains. All three genospecies were represented. Borreliae were administered mainly by both intravenous (about 10(6) to 10(9) spirochaetes) and intradermal (10(4)) routes, and on six occasions subcutaneously (10(3)) only. For infectivity control and comparison purposes mice and rabbits were inoculated simultaneously. Immune responses in cattle were monitored both with whole-cell sonicate enzyme-linked immunosorbent assay (IgG-ELISA) and indirect immunofluorescent assay (IgM-IgG-IFA). Five Finnish strains and the American strain B31 were used as antigens. No clinical signs of borreliosis were observed. Of the strains, 7/10 were interpreted by the immune responses to have caused relatively short-term subclinical infections of varying intensity. Borreliae could not be isolated from blood or other organ specimens of cattle. A rough estimate of the mean infectious dose in the conditions of experiments is 10(6) to 10(7) organisms. In conclusion, the overall result appears to argue a low susceptibility of cattle to clinical borreliosis, at least when infected by Finnish strains of the agent. Significant antigen-specific differences were observed both by ELISA and IFA in detection and quantification of immune responses. As a rule, the homologous antigen was found to be the most sensitive. Genospecies differences were mostly distinct. Antigens of two Borrelia garinii isolates proved practically equal in sensitivity, whereas major differences were displayed between two Borrelia afzelii antigens. In an IFA study, an American (B31) and a Finnish B. burgdorferi sensu stricto strain proved equally sensitive as antigens. In two relatively strong primary immune responses the antigen-specific measurement differences were such that diagnostically in a cross-sectional study only the homologous antigen or an antigen of the same genospecies would have been sufficiently sensitive to show a positive result.

Immunization with a polyvalent OspA vaccine protects mice against Ixodes ricinus tick bites infected by Borrelia burgdorferi ss, Borrelia garinii and Borrelia afzelii

Sequence variability of the outer surface protein (Osp) A among Borrelia burgdorferi sl species suggests that a monovalent OspA vaccine may not protect against the various Borrelia present in Eurasia. Here, we confirmed that a monovalent recombinant OspA (rOspA) vaccine does not protect mice against Ixodes ricinus mediated infection with B. burgdorferi ss, Borrelia garinii and Borrelia afzelii. However, when mice were vaccinated with a cocktail of various rOspA from these three species, they were protected, and all challenge ticks that fed on them were cleared of their spirochetes. These results showed that a multiple OspA antigens vaccine, compatible with human use, was very efficient at protecting mice against B. burgdorferi ss, B. garinii, and B. afzelii.

Resistance to tick-borne spirochete challenge induced by Borrelia burgdorferi strains that differ in expression of outer surface proteins

Hamsters were immunized with thimerosal-killed Borrelia burgdorferi 297 or a mutant of 297 (M297) that lacks the 49-kb linear plasmid and expression of outer surface proteins A and B (OspA and OspB). Ixodes scapularis nymphs infected with either the B. burgdorferi sensu stricto strain 297 or JMNT, similar in OspA and OspB but differing in OspC expression, were used to evaluate protection. In a homologous challenge, 24 hamsters were vaccinated, 8 each with 297 or M297 and 8 sham (adjuvant)-vaccinated controls. Hamsters vaccinated with either bacterin were completely protected against a natural tick bite or subcutaneous (s.c.) inoculation of 297. Borreliae were effectively eliminated from 80 to 90% of the 297-infected ticks that fed on four hamsters immunized with the 297 bacterin. Cultures of spirochetes isolated from the ticks that remained infected were infectious and induced joint inflammation in naive hamsters. There was no reduction of strain 297 spirochetes in ticks that fed on four hamsters immunized with M297, but the hamsters were protected. Results with the M297 bacterin indicate that proteins other than OspA or OspB can protect hamsters against a tick challenge without eliminating B. burgdorferi in the tick. In a heterologous challenge, 36 hamsters were vaccinated, 12 with each bacterin and 12 controls. None of the hamsters immunized with either bacterin were protected from a challenge involving JMNT-infected ticks, while two of four were protected against an s.c. challenge. Hamsters challenged s.c. with strain 297 spirochetes were protected. There was partial elimination of JMNT spirochetes in ticks that fed on the group of four hamsters immunized with the 297 bacterin, and infection rates were reduced by 50 to 60%. JMNT spirochetes reisolated from the ticks that fed on 297-vaccinated hamsters also remained infectious for hamsters. In the JMNT-infected ticks that fed on four M297-immunized hamsters, there was no decline in the proportion of infected ticks. Destruction of spirochetes in ticks that fed on the hamsters vaccinated with the 297 bacterin suggests that antibodies to OspA and OspB may have been responsible, since the mutant did not induce this activity.

Immunological and molecular variability of OspA and OspC. Implications for Borrelia vaccine development

Borrelia burgdorferi sensu lato, the etiological agent of Lyme borreliosis is considerably heterogeneous in Europe. Since the outer surface proteins OspA and OspC are the most promising candidates for a Borrelia vaccine the immunological heterogeneity of these proteins was investigated. By immunological analysis with monoclonal antibodies and sequence analysis of PCR amplified OspA and OspC at least seven and 16 different types, respectively, were found. Whereas skin isolates (n = 68) were quite homogeneous (84% belonged to OspA-serotype 2 or Borrelia afzelii), isolates from human cerebrospinal fluid and from ticks (n = 43 and n = 90 respectively) were highly heterogeneous in their OspA-serotypes with prevalence of the Borrelia garinii associated types (about 70%). OspA-type 4 was often found among isolates from cerebrospinal fluid (28%). In ticks type 4 OspA has not been detected by culture so far. However, as reported in a previous study, type 4 OspA could be detected in ticks by the highly sensitive PCR technique.

Diversity of OspA and OspC among cerebrospinal fluid isolates of Borrelia burgdorferi sensu lato from patients with neuroborreliosis in Germany

Neuroborreliosis is the most frequent manifestation of the second stage of Lyme borreliosis in Europe. However, only few isolates from the cerebrospinal fluid (CSF) have been characterized with controversial results. A large panel of 36 CSF isolates isolated over a 10-year period in Munich has now been analyzed for their OspA and OspC type, resulting in at least eight different types, respectively. Representatives of the different types cultivated from CSF in Munich have also been isolated from other geographical regions in Europe from CSF or ticks, suggesting a widespread distribution of pathogenic strains. A certain OspA type (type 4) was frequently observed in adults but rarely in children or ticks. Since OspA and OspC are the most promising candidates for a Borrelia vaccine, the considerable heterogeneity found among CSF isolates has important implications for development of a vaccine in Europe.

Involvement of CD4+ T lymphocytes in induction of severe destructive Lyme arthritis in inbred LSH hamsters

We determined that Borrelia burgdorferi-specific CD4+ T lymphocytes are responsible for the development of severe destructive Lyme arthritis and affect the production of borreliacidal antibody. Severe destructive Lyme arthritis was readily evoked in immunocompetent inbred LSH hamsters vaccinated with a whole-cell preparation of Formalin-inactivated B. burgdorferi sensu stricto isolate C-1-11 in adjuvant when challenged with B. burgdorferi sensu stricto isolate 297. When vaccinated hamsters were depleted of CD4+ T lymphocytes by the administration of monoclonal antibody GK1.5 and challenged, they failed to develop severe destructive arthritis. Similarly, nonvaccinated hamsters with or without the depletion of CD4+ T lymphocytes failed to develop severe destructive arthritis. In addition, depleting CD4+ T lymphocytes impaired the development of borreliacidal antibody in vaccinated and nonvaccinated hamsters challenged with the Lyme borreliosis spirochete. These findings show that CD4+ T lymphocytes are important for the recognition of arthritogenic and protective antigens of B. burgdorferi sensu lato isolates. Additional studies are needed to define the mechanisms responsible for the development of severe destructive Lyme arthritis and the production of borreliacidal antibody.

Protection of C3H/He mice from experimental Borrelia burgdorferi infection by immunization with a 110-kilodalton fusion protein

A 110-kDa Borrelia burgdorferi fusion protein, Escherichia coli expressing the fusion protein, transformed E. coli lacking the fusion protein insert, and lyophilized whole B. burgdorferi bacteria were compared for immunogenicity in C3H/He mice. Immunized mice were challenged with a variety of isolates from the United States or the European isolate P/Gau 3 weeks following the last inoculation. An average of 76.7% of the mice immunized with 25 micrograms of lyophilized whole B. burgdorferi cells were protected from infection, while 60% of the mice immunized with the 110-kDa fusion protein were protected. Whole E. coli bacteria expressing the fusion protein protected 57.7% of immunized mice against experimental challenge. Lower levels of protection occurred in mice challenged with the European isolate than in those challenged with isolates originating from the United States. These results demonstrate the potential of the 110-kDa fusion protein for use as a component of a subunit vaccine for prevention of Lyme borreliosis.

Abilities of OspA proteins from different seroprotective groups of Borrelia burgdorferi to protect hamsters from infection

The ability of vaccination with recombinant OspA from six seroprotective groups of Borrelia burgdorferi sensu lato to induce protection against infection with homologous and other Lyme spirochetes was examined in hamsters. Antisera generated against the OspA proteins of B. burgdorferi sensu stricto S-1-10 and C-1-11 (seroprotective groups 1 and 2, respectively), Borrelia afzelii BV1 (seroprotective group 4), and Borrelia garinii LV4 (seroprotective group 5) were able to kill the homologous spirochete in vitro but not other isolates. Surprisingly, antisera against B. afzelii PKo (seroprotective group 6) and B. burgdorferi sensu lato LV5 (seroprotective group 3) OspA proteins were unable to kill the homologous organism, although LV5 OspA antisera killed the heterologous isolates S-1-10 and LV4. In vivo vaccination studies supported the in vitro findings, confirming that vaccination with a single OspA protein does not provide complete protection against challenge with all Lyme disease spirochetes. In addition, OspA antibodies from some isolates may not protect against the homologous isolate. The induction of protective antibodies against other B. burgdorferi proteins may be necessary to insure a comprehensive Lyme disease vaccine.

Selection of variant Borrelia burgdorferi isolates from mice immunized with outer surface protein A or B

A nonclonal population of Borrelia burgdorferi N40 (passage 3) that survived protective immunity following challenge inoculation of outer surface protein (Osp) A- or B-hyperimmunized mice were characterized for the molecular basis of evasion of immunity. Two of six B. burgdorferi isolates, cultured from OspA-immunized mice, had antigenic diversity in the carboxyl terminus of OspA and did not bind to the protective OspA monoclonal antibody designated IXDII. However, OspA-immunized mice challenged with these variants were fully protected. Moreover, B. burgdorferi isolates with a point mutation in ospB, which results in a truncated OspB that does not bind to protective OspB monoclonal antibody 7E6C, were frequently enriched after infection of OspB-immunized mice. These studies suggest that the incomplete efficacy of an OspA- or OspB-based vaccine may be partly due to immunomediated in vivo selective pressure, resulting in the persistence of some spirochetes that do not bind to protective antibodies.

Linear chromosomes of Lyme disease agent spirochetes: genetic diversity and conservation of gene order

We have constructed physical and genetic maps of the chromosomes of 21 Lyme disease agent spirochetes from geographically diverse locations. All have linear chromosomes whose lengths range from 935 to 955 kbp, and all contain multiple linear plasmids in the 16- to 175-kbp size range. The locations of 11 gene clusters on the chromosomes of these different isolates are indistinguishable at the resolution achieved in this study, indicating that the members of this related group of species have highly conserved chromosomal gene orders. However, chromosomal restriction endonuclease cleavage site maps are unique for nearly all isolates. The 22 chromosomal maps currently available define eight classes of Lyme disease agents. Four of these correspond to the previously proposed species Borrelia burgdorferi, Borrelia garinii, Borrelia afzelii, and Borrelia japonica. In addition, the North American isolates 21038, DN127 c19-2, 25015, and CA55 typify four additional chromosomal types that are as phylogenetically distinct as the species listed above. These findings support the idea that comparison of restriction maps is currently the most robust and definitive method for determining overall chromosomal relationships among closely related bacteria. In the course of this work, we located on the chromosome the previously unmapped outer surface protein-encoding LA7 gene and genes homologous to the Escherichia coli priA, plsC, parE, and parC genes, and we have substantially refined the locations of the recA, fla, p22A, and flgE genes.

Borrelia burgdorferi-specific T lymphocytes induce severe destructive Lyme arthritis

This is the first documentation that Borrelia burgdorferi-specific T lymphocytes are involved in the pathogenesis of Lyme arthritis. We present direct evidence that T lymphocytes obtained from inbred LSH hamsters vaccinated with a whole-cell preparation of Formalin-inactivated B. burgdorferi sensu stricto isolate C-1-11 in adjuvant conferred on naive recipient hamsters the ability to develop severe destructive arthritis when challenged with B. burgdorferi sensu stricto isolates C-1-11 and 297. By contrast, recipients infused with normal T lymphocytes and challenged with B. burgdorferi sensu stricto isolates C-1-11 and 297 failed to develop severe destructive arthritis. The T lymphocytes transferred were obtained from the lymph nodes of vaccinated and nonvaccinated hamsters by depleting B lymphocytes by using monoclonal antibody 14-4-4s (< 1% B lymphocytes by flow cytometric analysis). The enriched T lymphocytes showed enhanced proliferation to stimulation with concanavalin A and failed to respond to lipopolysaccharide. Moreover, only the enriched T lymphocytes from vaccinated hamsters proliferated on exposure to a whole-cell preparation of B. burgdorferi sensu stricto isolate C-1-11 in the presence of mitomycin-treated syngeneic antigen-presenting cells. These results demonstrate that B. burgdorferi-specific T lymphocytes primed by vaccination with a whole-cell preparation of inactivated B. burgdorferi sensu stricto isolate C-1-11 in adjuvant are involved in the development of severe destructive arthritis. Additional experiments are needed to define the precise mechanism(s) responsible for the development of Lyme arthritis.

Vaccination against Lyme disease caused by diverse Borrelia burgdorferi

Diversity and mutations in the genes for outer surface proteins (Osps) A and B of Borrelia burgdorferi sensu lato (B. burgdorferi), the spirochetal agent of Lyme disease, suggests that a monovalent OspA or OspB vaccine may not provide protection against antigenically variable naturally occurring B. burgdorferi. We now show that OspA or OspB immunizations protect mice from tick-borne infection with heterogeneous B. burgdorferi from different geographic regions. This result is in distinct contrast to in vitro killing analyses and in vivo protection studies using syringe injections of B. burgdorferi as the challenge inoculum. Evaluations of vaccine efficacy against Lyme disease and other vector-borne infections should use the natural mode of transmission and not be predicated on classification systems or assays that do not rely upon the vector to transmit infection.

Assignment of Borrelia burgdorferi strains G25 and VS461 to the Borrelia garinii and Borrelia afzelii genospecies, respectively: a comparison of OspA protein sequences

The nucleotide sequence encoding the Outer Surface Protein A (OspA) from two Borrelia burgdorferi sensu lato isolates, G25 and VS461, has been determined. On the basis of a phylogenetic analysis, strains G25 and VS461 were respectively assigned to the B. garinii and B. afzelii genospecies. Comparative analysis of OspA proteins from 26 different B. burgdorferi sensu lato strains involved in Lyme disease indicated a higher heterogeneity in the B. garinii genospecies than in the two other genospecies, B. burgdorferi sensu stricto and B. afzelii.

Differential immune responses to Borrelia burgdorferi in European wild rodent species influence spirochete transmission to Ixodes ricinus L. (Acari: Ixodidae)

Immune responses to Borrelia burgdorferi and their influence on spirochete transmission to Ixodes ricinus were analyzed in the natural European reservoir hosts; i.e., the mouse species Apodemus flavicollis (yellow-necked mouse) and Apodemus sylvaticus (wood mouse) and the vole species Clethrionomys glareolus (bank vole), and, in addition, in the laboratory mouse strain NMRI. Naive and preimmunized rodents were infected either by artificially infected I. ricinus larvae or by intradermal injection of spirochetes. Independent of the species, all animals developed antibodies to various spirochetal antigens. However, antibodies to the outer surface proteins A (OspA) and B (OspB) were not found in recipients infected via ticks. Rodents of the genus Apodemus and of the NMRI strain showed higher levels of B. burgdorferi-specific antibodies than those of the species C. glareolus. The rate of spirochete transmission to noninfected ticks correlated with both the quality and quantity of spirochete-specific antibodies generated in the various species: high levels of spirochete-specific immunoglobulins correlated with low transmission rates. Furthermore, lower transmission rates were observed with rodents expressing antibodies to OspA and OspB (i.e., intradermally infected or immunized) than with those lacking these specificities (i.e., infected via ticks). The study provides evidence that transmission of B. burgdorferi from natural hosts to ticks is controlled by the specificity and quantity of spirochete-reactive antibodies and suggests that immunity to B. burgdorferi in natural reservoir hosts is an important regulatory factor in the horizontal transmission of B. burgdorferi in nature.

Development of destructive arthritis in vaccinated hamsters challenged with Borrelia burgdorferi

We present the first direct evidence that adverse effects, particularly severe destructive arthritis, can develop in vaccinated hamsters after challenge with Borrelia burgdorferi sensu lato isolates. Hamsters were vaccinated with a whole-cell preparation of Formalin-inactivated B. burgdorferi sensu stricto isolate C-1-11 in adjuvant. A severe destructive arthritis was readily evoked in vaccinated hamsters challenged with the homologous B. burgdorferi sensu stricto isolate C-1-11 before high levels of protective borreliacidal antibody developed. Once high levels of C-1-11 borreliacidal antibody developed, hamsters were protected from homologous challenge and development of arthritis. Vaccinated hamsters, however, still developed severe destructive arthritis when challenged with other isolates of the three genomic groups of B. burgdorferi sensu lato (B. burgdorferi sensu stricto isolate 297, Borrelia garinii isolate LV4, and Borrelia afzelii isolate BV1) despite high levels of C-1-11 specific borreliacidal antibody. Vaccines that contained whole spirochetes in adjuvant induced destructive arthritis, but this effect was not dependent on the isolate of B. burgdorferi sensu lato or the type of adjuvant. These studies demonstrate that caution is necessary when employing whole spirochetes in adjuvant for vaccination to prevent Lyme borreliosis. Additional studies are needed to identify the antigen(s) responsible for the induction and activation of arthritis and to define the immune mechanisms involved.

Protection of C3H/HeN mice from challenge with Borrelia burgdorferi through active immunization with OspA, OspB, or OspC, but not with OspD or the 83-kilodalton antigen

Recent advances in the development of animal models for Lyme borreliosis have provided means of identifying potential targets for the design of a subunit vaccine to prevent this disease. The C3H/HeN mouse model was used to study several Borrelia burgdorferi antigens from a single isolate for their ability to elicit borreliacidal and protective antibodies. The ospA, ospB, ospC, ospD, and 83-kDa genes from a California isolate, SON 188, were cloned and expressed in Escherichia coli as proteins fused to the C-terminal end of maltose-binding protein. Active immunization of mice with these fusion proteins elicited high titers of antibodies that recognized the homologous SON 188 antigens upon immunoblotting. Antibodies generated to the OspA and OspB fusion proteins, but not to the OspC, OspD, and the 83-kDa fusion proteins, demonstrated in vitro borreliacidal activity. Challenge of all actively immunized mice with 10(7) SON 188 spirochetes resulted in infection in all mice receiving the OspD or 83-kDa immunogens but not in any mice receiving the OspA, OspB, or OspC fusion proteins. These results demonstrate the potential of OspA, OspB, and OspC as components of a subunit vaccine for the prevention of Lyme borreliosis.

Ability of canine Lyme disease vaccine to protect hamsters against infection with several isolates of Borrelia burgdorferi

We used flow cytometry to determine levels of borreliacidal antibodies in hamsters after vaccination with a commercially available canine Lyme disease vaccine. In addition, we evaluated the ability of vaccinated hamsters to resist infection with several isolates of Borrelia burgdorferi. Borreliacidal antibodies could be detected 1 week after a primary vaccination, peaked at weeks 3 to 5, and then rapidly declined. One week after a booster vaccination, borreliacidal activity was detected at a dilution of 1:10,240, and it decreased fourfold by week 10 after the booster vaccination. Vaccinated hamsters were protected against infection with < or = 10(6) B. burgdorferi 297 organisms during the peak borreliacidal response (5 weeks after primary vaccination or 2 weeks after booster vaccination). However, hamsters were not fully protected from development of Lyme arthritis when the titer of borreliacidal antibodies was < 1:5,120. In addition, no significant borreliacidal activity was induced against B. burgdorferi C-1-11, LV4, or BV1, which belong to three other seroprotective groups. These studies demonstrate that vaccination with the canine Lyme disease vaccine induces protective antibodies against B. burgdorferi 297. However, significant levels of borreliacidal antibodies are not produced until 5 weeks after vaccination, and protection is short-lived. In addition, no borreliacidal activity was induced against other isolates of B. burgdorferi. Because of this, the incorporation of multiple isolates or protein subunits may be necessary to increase the effectiveness of future vaccines.

Lyme disease: laboratory diagnosis and serologic testing

Although identified less than 20 years ago, Lyme disease has proved to be the most common tick-borne disease in the United States: some 10,000 cases were reported in 1992. In some cases the disease may be transitory and of little consequence but in others it may become chronic and severely disabling. Accurate diagnosis is, therefore, of great importance but, as this article shows, laboratory testing techniques still need improvement.